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Help with coolant hose bypass mod

28K views 24 replies 13 participants last post by  asad101090 
#1 ·
While searching something else I read about bypassing the coolant hoses that heat the intake manifold. Can't find that thread now, is this a worthwhile mod and can someone link back to it?

thanks
 
#4 ·
We concern ourselves with providing cool air from outside the engine bay and improving the airflow into the airbox by removing the resonators and adding a K&N and/or a snorkel, then the air flows through an intake manifold that is intentionally heated to coolant temp. In my climate there's no need to heat the intake. This is a fairly popular mod with the LS1 etc crowd. No downside and any possible gain for little cost is welcome with the underwhelming 3.3!
 
#6 ·
The heater core bypass requires only a 5/8 inch hose union and a couple of hose clamps. The hoses are the ones that go through the firewall on the passenger side. I have done this bypass because my heater core fitting cracked and leaks, and I don't have time to replace it now. You MAY have to cut the hoses off to get them off the nozzles, but they are flexible enoguh to bend end to end to connect with a union, and low cost to replace if needed.
 
#25 ·
I had tried doing the same bypass due to the same reason of cracked and leaks, now however my truck has started to shake and jerk a lot while riding smooth at 1500-2000 rpm, however the mechanics have mentioned it could be an engine rebuilt. I wanted to check would this had caused the sudden jerks as if crankshaft gone bad or gear box. It would even switch off at red light as well. Dont wanna drop to the stealership yet as well. any sugestions
 
#7 ·
Hi, thanks for the reply. I think you misunderstand what I'm talking about, I'm not looking to bypass the heater core. I'm looking to bypass the coolant lines that heat the upper intake manifold and throttle body. The lines through the firewall go to the heater core. There are lines behind the manifold that tee off off the heater core lines and go into the manifold.

Was going to start gathering temp data with an infrared thermometer and buy one of the IMSs offered on the group buy last week but a family emergency kept me away until now.
 
#8 ·
Take a look at the cooling circuit from the FSM. The coolant that heats the intake manifold and TB comes directly from a cylinder head meaning it's at it's highest temp before it goes back to the rad or the heater circuit. The harder you run the hotter the water exiting the engine is and the hotter your TB and intake are going to get. The IMS is only going to eliminate part of the heat going into the intake manifold.
 
#9 · (Edited)
Old Threads:

http://www.clubxterra.org/forums/showthread.php?t=5016&page=2

http://xterrafirma.com/forums/viewt...sid=bf8a860d1f114ad47748fdc6b1832b40&start=15


First question...Intake Manifold Collector...that is the upper manifold? Double checked with courtesy parts, and looks like the manifold is the lower portion, the collector is the upper. That is what I am assuming in the schematic.

So that schematic shows that the coolant enters the intake manifold...and then splits 3 ways out of the manifold 1) Water outlet housing, 2) Heater, 3) Throttle Body/Manifold Collector

I see 2 options:

1) Bypass all of the intake manifold/throttle body/collector. This is the first graphic below. You would basically need to find the line from the cylinder head, and put a 3 way splitter on the end. Route one line to the heater output, bypassing the collector and the throttle body. Route one line around the manifold and to the heater input. Route another line to the water outlet housing. This bypasses all of the intake.

Since we don't have a thermal spacer for the lower manifold off of the cylinder heads, no real need to bypass the lower manifold coolant. Even if we bypass it, it will get heat soaked from the engine. We could leave the lower manifold coolant, and rely on the spacer to keep the collector cool.

2) Bypass just the throttle body and the upper collector since that is what is thermally isolated. Seems you would just need to remove the line going into the throttle body, and connect it to the line going out of the manifold collector. This would bypass the throttle body and collector, but maintain the coolant in the lower manifold. This seems easier.

Disclaimer...I have never done this before...not sure exactly how that translates to specific hoses on the car. I am not an expert, but have a bit of experience in schematics and mechanical systems. This makes sense to me.

Another thing to consider: The more metal things we bypass, the less heat is absorbed by the manifolds, which means more heat in the coolant. We are also losing coolant capacity as we no longer have the volume of coolant inside the manifolds/collectors. This means the stock cooling system has to reject more heat through the radiator since it isn't absorbed into manifolds and throttle bodies...and it also has less coolant to do that with. Super charged radiator may be a good addition, too.
 

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#10 ·
Hi. We're on the same page. It seems your option #2 makes the most sense and should be easiest. The TB input is easy to find and I suspect the collector input is just left of the PCV valve. Haven't positively ID'd the collector output hose yet. 1 length of hose, 2 barbed connectors and 4 clamps should do it. Going to try to get it figured out and do the bypass first before the IMS since it's easier to reverse.
 
#14 · (Edited)
Sure did, it's easy. You'll have to disable the cold high-idle wax solenoid as well or you'll always have an 1800 rpm idle. Easy to do as well. I've been running it bypassed for 2 months and see no downside at all, at least in my climate here in central Az. Something else in the throttle body gives a 1200 rpm cold idle that drops to 6-700 when warm. I think it's the 2nd piece of the puzzle if you do the IMS. Will do a how-to in the next day or 2. My IMS is sitting on a shelf, just didn't feel like cutting and replacing hoses to get it in.

Love your Atomic Orange X...trade?
 
#15 ·
If that's the smurf blue from 2002 I'd be tempted! That's always been my second favorite X color, and I must say I see more orange ones driving around.

And did you do the coolant hoses at the back of the intake as well? Or just the throttle body ones? I'm more interested in bypassing the ones in the back because I have a leak there and no matter what I do I can't get everything on tight enough back there to stop it.

What are the benefits of doing the throttle body hoses? Being in Tucson, I expect I'd have the same results as you.
 
#16 ·
I did this when I stripped the first two threads on the #6 spark plug in the head I hate Nissan for putting that damn thing back there so far luckily I had a friend who is an Army machinist and was able to retap with same diameter tap and fix it. Any way the video I found about this mod is pretty straight forward unless you live in a climate area that gets subzero temps there in no need to heat intake or plenum area. DD196X is right its modders 101 cold dense air is better. It’s an easy thing to do disconnect plenum you will fight with two hoses in the back left if facing vehicle. One is inlet and one is outlet for the plenum. After removal I took an 8-10 inch piece of heater hose same dimensions of the original put it on steel tubing for inlet with a regular hose clamp and then attached it to steel tubing of outlet side with a hose clamp. Put everything back together and done and done.
 
#17 ·
Yes I did option 2 on my Land Rover Disco II. It is very similar. The Rover would leak coolant around the the throttle body. I think the only thing that is used for is in case it freezes. The throttle can stick if it does. I live in Ky. it gets very cold sometime but never had a problem with it Just remember to keep it circulating instead of blanking it.
 
#19 ·
FYI, I have found it is important to keep the heater in the route, as if your thermostat malfunctions, you can use the heater to dump heat from the system and keep going for a while until you can replace your thermostat, instead of being stuck on the side of the road waiting for it to cool.
 
#20 ·
I think your missing the point of this thread. They aren't talking about by passing the Heater Core. They are removing coolant from going to the Intake manifold. Which in turn makes a lot of this easier to access and less chance of one of those in the ass TB hoses leaking and then having to be fixed.

I just used two hose caps and will replace every year.

But this cold idle sensor...can I just unhook it? Anyone know what the plug looks like?
 
#21 ·
I just got around to doing this mod. Intake manifold spacer had been sitting in my tool box for like 2 years now. Finally got motivated because those two stupid hoses at the back were leaking coolant which was getting annoying. I wasn't initially going to do the bypass, but the reasons I did:

It eliminates like 6 other potential hose junctions that could leak.
It makes it easier to get the intake manifold off for other services.
Those rear coolant hoses are a B!TCH to get to the hose clamps...so I got a 12" length of hose and just connected them together. My hope is that it will never have to be touched again, even during service.

One follow up question:

I saw comments about the cold idle wax solenoid needing to be modified to have a controlled idle RPM.

Can someone elaborate on what exactly needs to be done?
 
#24 · (Edited)
Hah....that's funny. That's my video!

I will say that I no longer have the intake manifold spacer installed on my truck, and I no longer have the coolant bypassed.

The IMS didn't make any difference that I could notice at all. It never fit well with the copper EGR tube, made the spark plug wires not fit properly with the added height of the intake manifold collector, and just added complexity that wasn't needed.

I un-did my coolant bypass mod when I was having some over-heating trouble. I was doing timing belt and cam shaft install anyway, so decided to replace all the stock rubber hoses anyway. I don't think the bypass was the cause of me having over-heating issues, though. The only benefit of the bypass mod is so you won't have to mess around with those hoses ever again. If I had to go into the engine / manifold for some reason, I would consider bypassing it again...but it didn't cause any noticeable improvement.
 
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